The Chinese fighter is accused of aggression when locking fire radars into Taiwan F-16 fighter jets during a meeting last month.

China held three air force exercises last month near Taiwan, forcing the island defenders to twice send surveillance or chasing aircraft, two Taiwanese government sources who spoke on condition of anonymity today revealed.

In one such encounter, Chinese fighters turned on fire control radars and locked targets on Taiwanese fighters. In combat, this lock-in action is the first step of launching a missile at the target. "This is a very serious provocation," the source said.

Taiwanese armed forces said they did not know about the incident, but insisted they always fully grasp the movements of Chinese troops near the island.

China's Ministry of Defense did not comment on the information.

Fire control radars are used to accurately locate targets, providing guidance parameters for guided missiles and ammunition. The activation of the fire radar and target lock usually only takes place when one side is ready to fire in combat, and is considered a serious provocation in peacetime.

Modern aircraft and warships are equipped with irradiation warning systems that allow them to determine if an enemy is being detected and locked onto a target by radar.

Last month, the Chinese Air Force dispatched the plane to the island of Taiwan many times, including the H-6K bomber crossing the median line, the boundary is implied as the line separating the Taiwan Strait. Eastern Military Region spokesman Zhang Chunhui said it was a "patrol operation in combination with a completely legal practice exercise."

China considers Taiwan a part of its territory waiting for reunification, including by force if necessary. Beijing has recently conducted air and naval exercises around the island of Taiwan, with the participation of the most modern payroll equipment such as Su-35S multi-function fighters and stealth aircraft. J-20, H-6K strategic bomber and Liaoning aircraft carrier.